1. Field of the Invention
The present invention relates generally to the stirring of sample materials and, more particularly, to magnetic stirrers for containers which hold the sample material.
2. Description of the Prior Art
U.S. Pat. No. 4,157,871 discloses a nephelometric system for the assay of antigens and antibodies supported within cylindrical glass containers. In such analysis, an antigen and an antibody are combined in the container and are stirred by a magnetic stirring element within the container. The stirring element is rotated by a motor-driven permanent magnet outside of the container and magnetically coupled to the stirring element. The reaction which results between the combined sample components produces a precipitate which increases in quantity and turbidity as the reaction progresses. The system measures the amount of light scattered by the precipitate to derive quantitative or qualitative information about the antigen or antibody sample components. In this system it is preferred to stir the reactants while measuring light scatter in order to sweep all precipitate particles past the detector field of view. This minimizes errors which could otherwise result due to increased scatter from large particles lodging motionless in the detector field of view.
The magnetic stirring arrangement for the foregoing system is similar to that in FIG. 1 of U.S. Pat. No. 3,784,170. In this regard a magnetic stirring bar is horizontally disposed in the bottom of a cylindrical glass sample container. A rotating permanent magnet magnetically coupled to the stirring element is positioned below the container and is rotated by a drive motor in a horizontal plane to correspondingly rotate the stirring bar inside the container. While the foregoing magnetic stirring arrangement has proved satisfactory in the foregoing nephelometric assays, its use has been restricted to sample containers which remain stationary at the measuring station during an optical measuring interval.